Method for Producing a Stimulation Electrode

ABSTRACT

A stimulation electrode is provided having an electrically conducting electrode base member which is partially covered with an electrically insulating ceramic layer. The ceramic layer is formed of an oxide and/or an oxynitride of at least one metal of the group of titanium, niobium. tantalum, zirconium, aluminum and silicon. Various methods are provided for production of the stimulation electrode, including methods in which the ceramic layer is formed in situ by a thermal, chemical or electrochemical oxidation or oxynitridation process. The stimulation electrode may be used as a cardiac pacemaker electrode, a neuro-stimulation electrode, or another human implant.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent application Ser. No. 10/735,069 filed on Dec. 12, 2003, entitled “Stimulation Electrode and Methods of Making and Using Same,” now U.S. Pat. No. 7,421,299.

BACKGROUND OF THE INVENTION

The invention is directed to a stimulation electrode with an electrically conducting electrode base member, which is partially covered with an electrically insulating ceramic layer, wherein the ceramic layer is formed from an oxide and/or an oxynitride of at least one of the metals selected from the group of titanium, niobium, tantalum, zirconium, aluminum, and silicon. The invention is further directed to the production of such a stimulation electrode and the use of such a stimulation electrode.

European published patent application EP 1 169 972 A1 discloses a catheter, which is equipped with a stimulation electrode. An electrically insulating and thermally conductive layer is arranged in the region of the stimulation electrode and can be formed of ceramic, among other things. The thickness of the electrically insulating and thermally conductive layer is <10 μm.

European Patent EP 0 620 024 B1 discloses stimulation electrode, which has a high-ohmic insulating layer on the electrode tip. A diamond-like carbon, which is extremely biocompatible, is particularly preferred here. The diamond-like carbon can be deposited using a laser, among other things. It is furthermore disclosed that the entire electrode head may be coated with a diamond-like carbon layer and thereafter the stimulation surfaces may be freed, as desired, by photoetching.

U.S. Pat. No. 6,298,272 B1 discloses a cardiac pacemaker electrode, which is provided with an insulating coating in the region of the electrode tip. The insulating coating here can be formed, for example, by dipping, printing, spraying on, painting on, and resist techniques.

International patent application publication WO 98/31419 discloses a cardiac pacemaker electrode, in which the electrode tip has an annular, electrically insulating sheathing. Plastics or elastomers, particularly silicone rubber, are disclosed here as materials for this sheathing.

German published patent application DE 35 18 317 A1 discloses a stimulation electrode, which is partially coated with insulating material. Plastic is disclosed here as the coating material.

BRIEF SUMMARY OF THE INVENTION

The invention now has as an object the provision of a stimulation electrode with very good biocompatibility and high long-term corrosion resistance and which at the same time can be produced rapidly and inexpensively.

The object is attained for the stimulation electrode set for the at the outset in that the electrode base member is further coated, at least partially, with an electrically conducting layer of titanium nitride, niobium nitride, tantalum nitride, zirconium nitride, aluminum nitride, silicon nitride, vanadium nitride, iridium oxide, or an alloy of platinum and iridium, wherein the iridium portion of the alloy is ≧21 wt. % and the platinum portion of the alloy is ≧ about 100 ppm.

These materials have a particularly good biocompatibility and can be applied with excellent adhesion to electrically conducting electrode base members. The following description of suitable production methods for the ceramic layer shows that these materials can be used in a simple and inexpensive manner.

In particular, it has been found to be advantageous if the electrode base member here is formed of titanium, tantalum, gold, carbon, platinum, iridium, a platinum-iridium alloy, an alloy based on cobalt and/or nickel, or stainless steel.

The ceramic layer can then be applied on the electrically conducting layer. However, the ceramic layer can also be applied adjacent to the electrically conducting layer on the electrode base member.

It has furthermore been found advantageous to coat the electrode base member, at least partially, with an electrically conducting layer of titanium nitride or with a titanium nitride layer. The ceramic layer here can then be applied both on the electrically conducting layer of titanium nitride and also adjacent the electrically conducting layer of titanium nitride on the electrode base member.

It is advantageous here if the electrically conducting layer of titanium nitride is at least partially covered with at least one oxidation protection layer on its side facing away from the electrode base member. This is of particular advantage when the stimulation electrode is to be used with anodic polarity, since the long-term durability of the stimulation electrode is significantly increased thereby.

The ceramic layer here can be applied on the at least one oxidation protection layer, or instead adjacent the electrically conducting layer of titanium nitride, and the at least one oxidation protection layer can be applied on the electrode base member.

It is furthermore possible for the ceramic layer to be applied adjacent the at least one oxidation protection layer on the electrically conducting layer of titanium nitride.

It has been found to be particularly advantageous for the at least one oxidation protection layer to be formed from at least one element of the group platinum, iridium, and gold. However, it is also possible to form the oxidation protection layer of an oxide, a carbide, a nitride, or a polymer, wherein the at least one oxidation protection layer reduces the impedance electrode base member coated with the electrically conducting layer of titanium nitride, or at most increases it to a value which is smaller than the impedance of the uncoated electrode base member.

The thickness of the oxidation protection layer is advantageously in the range of about 500 nm to about 5 μm.

Thicknesses of about 1 nm to about 20 μm have been found to be advantageous for the ceramic layer; wherein the layer thickness depends heavily on the production method used for forming the ceramic layer.

The ceramic layer can have a surface which is closed in itself or instead can be formed by plural independent surfaces.

The object is attained for a first method of manufacture of the stimulation electrode in that the ceramic layer is formed by a PVD (physical vapor deposition) method, a CVD (chemical vapor deposition) method, or a dip, spray, or sol-gel method. As suitable PVD methods, for example, cathode sputtering, thermal vaporization, electron beam vaporization, or arc vaporization may be considered.

The object is attained for a second method of production of the stimulation electrode, in that the ceramic layer is formed by depositing a metallic layer of titanium and/or niobium and/or tantalum and/or zirconium and/or aluminum and/or silicon, and in that a thermal or electrochemical or chemical oxidation or oxynitriding of the metallic layer subsequently takes place. This method can be performed particularly simply and cost-effectively.

The object is attained for a third method of production of a stimulation electrode with a titanium electrode base member, in that the ceramic layer is formed by the electrode base member being partially oxidized, thermally or chemically, to titanium oxide.

The object is attained for a fourth method of production of a stimulation electrode with a tantalum electrode base member, in that the ceramic layer is formed by the electrode base member being partially oxidized, thermally or chemically, to tantalum oxide.

The third and fourth methods according to the invention make possible the direct formation of the ceramic layer from the material of the electrode base member, so that a separate application of material for the ceramic layer is not required.

The object is attained for a fifth method of production of a stimulation electrode, in which the electrode base member is at least partially covered with an electrically conducting layer of titanium nitride, in that the ceramic layer is formed by the electrically conducting layer of titanium nitride being partially oxidized, thermally or electrochemically, to titanium oxide, wherein the oxidation comprises at least a portion of the layer thickness of the electrically conducting layer of titanium nitride.

For the second through fifth methods according to the invention, it has been found to be particularly advantageous to perform the thermal oxidation with a laser.

For the first through fifth methods according to the invention, it has further been found to be advantageous if the ceramic layer is first formed over the full surface on the uncoated or coated electrode base member, and it is then partially removed again by etching.

The use of the stimulation electrode according to the invention is ideal as a cardiac pacemaker electrode, neuro-stimulation electrode, retinal implant, cochlear implant, or in another human implant.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

FIG. 1 is a schematic side view of an electrode base member made of titanium with a ceramic layer;

FIG. 2 is a schematic side view of an electrode base member made of stainless steel with a ceramic layer;

FIG. 3 is a schematic side view, partially in section, of a stimulation electrode according to the invention with a titanium electrode base member having a titanium nitride coating;

FIG. 4 is a schematic side view, partially in section, of a stimulation electrode according to the invention with a platinum-iridium alloy electrode base member; and

FIGS. 5-8 are schematic side views, partially in section, of stimulation electrodes according to the invention with a titanium electrode base member having a titanium nitride coating and an oxidation protection layer.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an intermediate product 1 in the production of the stimulation electrode according to the invention with a titanium electrode base member 2, which was superficially oxidized by a laser to a ceramic layer 3 of titanium oxide.

FIG. 2 shows and intermediate product 1 a in the production of the stimulation electrode according to the invention with a stainless steel electrode base member 2 a. A ceramic layer 3 a of aluminum oxide, formed by electron beam vaporization, is applied on the electrode base member 2 a.

FIG. 3 shows a stimulation electrode 1 b with a titanium electrode base member 2 b. The electrode base member 2 b here is coated with a titanium nitride layer 4 b. The titanium nitride layer 4 b was partially oxidized by electrochemical oxidation to titanium oxide with formation of the ceramic layer 3 b.

FIG. 4 shows a stimulation electrode 1 c with an electrode base member 2 c of a platinum-iridium alloy with 10 wt. % iridium content. The electrode base member 2 c here is covered with a layer 4 c of iridium oxide. A ceramic layer 3 c of tantalum oxide is applied on the layer 4 c and was formed by the vapor deposition of metallic tantalum and subsequent thermal oxidation of the tantalum.

FIG. 5 shows a stimulation electrode 1 d with a titanium electrode base member 2 d. The electrode base member 2 d is covered with a titanium nitride layer 4 d, which in turn is overcoated with an iridium oxidation protection layer 5 d. A titanium oxide ceramic layer 3 d, applied directly on the electrode base member 2 d, is arranged adjacent to the titanium nitride layer 4 d and also the iridium oxidation protection layer 5 d. The ceramic layer 3 d here is formed of titanium oxide, which was formed by application of metallic titanium and subsequent thermal oxidation by a laser.

FIG. 6 shows a stimulation electrode I e with a titanium electrode base member 2 e. The electrode base member 2 e here is covered with a titanium nitride layer 4 e, which in turn is partially covered with a platinum oxidation protection layer 5 e. In the region in which the oxidation protection layer 5 e does not cover the titanium nitride layer 4 e, a titanium oxide ceramic layer 3 e is formed by oxidation of the titanium nitride layer 4 e.

FIG. 7 shows a stimulation electrode 1 f with a titanium electrode base member 2 f, which is coated with a titanium nitride layer 4 f. The titanium nitride layer 4 f is partially coated with an iridium oxidation protection layer 5 f. In the regions of the titanium nitride layer 4 f not covered with the oxidation protection layer 5 f, the titanium nitride layer 4 f is superficially converted into a titanium oxide ceramic layer 3 f by thermal oxidation with a laser.

FIG. 8 shows a stimulation electrode 1 g with a titanium electrode base member 2 g, which is covered with a titanium nitride layer 4 g. The titanium nitride layer 4 g is further covered with a platinum-iridium alloy oxidation protection layer 5 g. A ceramic layer 3 g of zirconium oxide, formed by a CVD method, is applied on the oxidation protection layer 5 g.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims. 

1. A method for producing a stimulation electrode comprising an electrically conducting electrode base member partially covered with an electrically insulating ceramic layer, wherein the ceramic layer (3, 3 a, 3 b, 3 c, 3 d, 3 e, 3 f, 3 g) is formed of an oxide and/or an oxynitride of at least one metal selected from the group consisting of titanium, niobium, tantalum, zirconium, aluminum, and silicon, and wherein the electrode base member (2, 2 a, 2 b, 2 c, 2 d, 2 e, 2 f, 2 g) is further at least partially coated with an electrically conducting layer (4 b, 4 c, 4 d, 4 e, 4 f, 4 g) comprising at least one material selected from the group consisting of titanium nitride, niobium nitride, tantalum nitride, zirconium nitride, aluminum nitride, silicon nitride, vanadium nitride, iridium oxide, and an alloy of platinum and iridium, wherein the iridium portion of the alloy is ≧21 wt. % and the platinum portion of the alloy is ≧ about 100 ppm, wherein the ceramic layer is formed by a method selected from the group consisting of PVD, CVD, dipping, spraying, and sol-gel.
 2. The method for producing a stimulation electrode according to claim 1, wherein the ceramic layer (3, 3 a, 3 b, 3 c, 3 d, 3 e, 3 f, 3 g) is formed by depositing a metallic layer comprising at least one metal selected from the group consisting of titanium, niobium, tantalum, zirconium, aluminum, and silicon, and the deposited metallic layer is subsequently subjected to a thermal oxidation, electrochemical oxidation, chemical oxidation, or oxynitridation process.
 3. The method for producing a stimulation electrode according to claim 1, wherein the electrode base member (2, 2 a, 2 b, 2 c, 2 d, 2 e, 2 f, 2 g) is made of titanium, and the ceramic layer (3, 3 a, 3 b, 3 c, 3 d, 3 e, 3 f, 3 g) is formed by at least partially oxidizing the titanium electrode base member (2, 2 a, 2 b, 2 c, 2 d, 2 e, 2 f, 2 g) to titanium oxide by thermal or electrochemical oxidation.
 4. The method for producing a stimulation electrode according to claim 1, wherein the electrode base member (2, 2 a, 2 b, 2 c, 2 d, 2 e, 2 f, 2 g) is made of tantalum, and the ceramic layer (3, 3 a, 3 b, 3 c, 3 d, 3 e, 3 f, 3 g) is formed by at least partially oxidizing the tantalum electrode base member (2, 2 a, 2 b, 2 c, 2 d, 2 e, 2 f, 2 g) to tantalum oxide by thermal or electrochemical oxidation.
 5. The method for producing a stimulation electrode according to claim 1, wherein the electrically conducting layer is made of titanium nitride and the ceramic layer (3, 3 a, 3 b, 3 c, 3 d, 3 e, 3 f, 3 g) is formed by at least partially oxidizing the titanium nitride electrically conducting layer (4 a, 4 d, 4 e, 4 f, 4 g) to titanium oxide by thermal or electrochemical oxidation, and wherein the oxidation includes at least a portion of a layer thickness of the titanium nitride electrically conducting layer (4 d, 4 e, 4 f, 4 g).
 6. The method for producing a stimulation electrode according to claim 1, wherein the electrically conducting layer is made of titanium nitride and the ceramic layer (3, 3 a, 3 b, 3 c, 3 d, 3 e, 3 f, 3 g) is formed by at least partially oxidizing the titanium nitride electrically conducting layer (4 a, 4 d, 4 e, 4 f, 4 g) to titanium oxide by thermal or electrochemical oxidation, and wherein the oxidation includes at least a portion of a layer thickness of the titanium nitride electrically conducting layer (4 d, 4 e, 4 f, 4 g).
 7. The method according to claim 2, wherein the thermal oxidation takes place by a laser.
 8. The method according to claim 3, wherein the thermal oxidation takes place by a laser.
 9. The method according to claim 4, wherein the thermal oxidation takes place by a laser.
 10. The method according to claim 5, wherein the thermal oxidation takes place by a laser.
 11. The method according to claim 6, wherein the thermal oxidation takes place by a laser.
 12. The method according to claim 1, wherein the ceramic layer (3, 3 a, 3 b, 3 c, 3 d, 3 e, 3 f, 3 g) is first formed on an entire coated or uncoated surface of the electrode base member (2, 2 a, 2 b, 2 c, 2 d, 2 e, 2 f, 2 g), and is then partially removed again by etching. 